Electronic structures and long-range electron transfer through DNA molecules

Quantum chemical calculation on an entire molecule of segments of native DN A was performed in an ab initio scheme with a simulated aqueous solution en vironment by overlapping dimer approximation and negative factor counting m ethod. The hopping conductivity was worked out by random walk theory and co mpared with recent experiment. We conclude that electronic transport in nat ive DNA molecules should be caused by hopping among different bases as well as phosphates and sugar rings. Bloch type transport through the delocalize d molecular orbitals on the whole molecular system also takes part in the e lectronic transport, but should be much weaker than hopping. The complement ary strand of the double helix could raise the hopping conductivity for mor e than 2 orders of magnitudes, while the phosphate and sugar ring backbone could increase the hopping conductivity through the base stacks for about 1 order of magnitude. DNA could transport electrons easily through the base stacks of its double helix but not its single strand. Therefore, the domina te factor that influences the electronic transfer through DNA molecules is the pi stack itself instead of the backbone. The final conclusion is that D NA can function as a molecular wire in its double helix form with the condi tions that it should be doped, the transfer should be a multistep hopping p rocess, and the time period of the transfer should be comparable with that of an elementary chemical reaction. (C) 2000 John Wiley & Sons, Inc.